The use of radar to determine range and velocity of objects in an environment is important in a number of applications including automotive radar and gesture detection. A radar system typically transmits a signal and listens for the reflection of the signal from objects in the environment. By comparing the transmitted signal with the received signal, a radar system can determine the distance to an object. Using multiple transmissions, the velocity of the object can be determined. Moreover, using multiple transmitters and receivers, the location (angle) of the object can also be determined.
There are several types of waveforms used in different types of radar systems. One type of waveform or radar signal is known as a frequency-modulated continuous waveform (FMCW). In an FMCW-type radar system, the transmitter of the radar system sends a continuous signal in which the frequency of the signal varies. This is sometimes called a chirp radar system. Mixing (multiplying) a waveform reflected from an object (also known as a target) with a replica of the transmitted signal results in a CW signal with a frequency that represents the distance between the radar transmitter/receiver and the target. By sweeping up in frequency and then down in frequency, the Doppler frequency can also be determined.
There is a continuous need for improved radar techniques that achieve good range performance without excessive transmitter power, which permit multiple users to share the spectrum, and which achieve an improved tradeoff between instantaneous bandwidth occupancy and range resolution.